PC case fans come in various sizes, from compact 80 mm units right up to hulking 200 mm airflow monsters. Each fan size has its strengths and weaknesses, ideal for specific use-cases. If you’re curious about the most common case fan sizes and where you’ll likely use them, this quick guide is for you.
The Most Common PC Fan Sizes
40 mm Fans
The first three case fan sizes on our list are uncommon at best, only appearing in small PC cases, lower-end CPU coolers, and non-PC enclosures such as NAS units. Some server rack units also use these fans, especially 40 mm units. Unless you’re building in some specific HTPC and Mini-ITX cases, you likely won’t ever need to shop around for these fans.
40 mm fans are the smallest size of computer case fan commercially available. Not many companies make these, and even fewer cases will be tiny enough to be limited to fans this small.
However, many single-unit rack devices (such as servers and network switches) take 40 mm fans, which is where you’re most likely to encounter these tiny fans. 40 mm fans usually run at super-high RPMs to provide enough cooling for passively-cooled internal components; Arctic’s S4028-6K, for example, runs at a maximum of 6000 RPM.
Some pure server-grade cooling fans can hit 8000 RPM or more. These speeds make 40 mm server fans likely the noisiest case fans you’ll encounter, as shown in videos like this one.
80 mm Fans
80 mm fans are a significant step up in size from 40 mm fans, and are comparatively much more common. You’ll most likely spot (or use) 80 mm fans in Mini-ITX and HTPC cases. These cases’ small dimensions mean they don’t always have room for the more standard 120 and 140 mm fans, so they opt for 80 mm fans in certain positions.
The SilverStone GD-09B, for example, uses two 80 mm exhaust fans in place of a standard 120 or 140 mm fan to make room for the motherboard I/O shield and eight expansion slots. You’re also likely to see 80 mm fan mounts in cases used by large-scale OEM manufacturers like Dell and HP for their prebuilts.
80 mm fans are also standard on low-end and compact CPU coolers. These coolers aren’t competing with high-quality tower-style CPU coolers; instead, they’re for use in constrained or low power consumption situations where the 80 mm fans’ relatively weak performance is less of an issue.
92 mm Fans
92 mm fans are likely the least common of the “typical” fan sizes, with few PC cases using this fan size. Like 80 mm fans, though, they’re slightly more common in prebuilts. Some of Dell’s XPS gaming desktops use 92 mm intake fans; the Dell XPS 8940, for example, takes either a single 92 mm or two 80 mm exhaust fans, depending on the GPU.
These fans also feature in some CPU coolers, including the Intel stock cooler. You can also spot 92 mm fans in some tower coolers, presumably to reduce size and cost. ID-COOLING’s SE-914-XT tower uses a 92 mm fan, for example.
However, the most common use of 80 and 92 mm fans is likely in compact, actively-cooled electronics. For example, some Synology NAS units use 80 and 92 mm fans, as do many SFX PSUs.
120 mm Fans
The following two fan sizes are the most common computer case fan sizes in modern PCs. If you’re shopping for fans, you’re probably shopping for one of these.
The 120 mm fan is almost the standard case fan size; from colossal super towers like the Corsair Obsidian 1000D down to compact Mini-ITX cases like the InWin A1, you’ll find 120 mm fan support almost everywhere. They’re arguably the middle-ground size for modern desktop PCs.
And it’s not just cases, too; many CPU coolers, be it tower coolers or AIOs, also use 120 mm fans to cool your CPU. Medium-sized tower coolers like the ever-popular Cooler Master Hyper 212 use 120 mm fans, as do 120, 240, 360, and 480 mm AIOs.
120 mm fans are generally the workhorse size: they’re usable in almost every PC case and offer significantly better cooling performance than the smaller case fan sizes. If you need additional 120 mm fans to add to your PC case, check out our list of the best 120 mm case fans.
140 mm Fans
140 mm fans are a small but significant step up from 120 mm fans, fast becoming the new standard for larger mid- and full-tower cases. This is especially true with airflow-focused cases like the Phanteks P400A, which can take advantage of the better airflow and static pressure performance that 140 mm fans provide.
Most tower cases will support both 120 and 140 mm fans on most (if not all) fan mounts, making the two essentially interchangeable as far as compatibility and usability go. 140 mm fans also see use in some of the larger dual-tower CPU coolers like the Noctua NH-D15, as well as 140, 280, and 420 mm AIOs.
140 mm fans can perform similarly to—or better than—120 mm fans at a lower fan speed and noise levels, making them better choices in cases that support them. Those looking to optimize their PC’s airflow without increasing noise levels too much will likely find 140 mm fans the better option.
Are you shopping around for 140 mm fans? Check out our list of the best 140 mm fans for some great suggestions.
180 mm Fans
Now we get on to the first of the rarely-seen larger fans of the cooling fan world, the 180 mm fan. These fans are huge compared to even 140 mm fans, with airflow performance to match. These are exclusively used as case fans since there isn’t a radiator or CPU tower cooler large enough to support one of these.
The main appeal of 180 and 200 mm fans is the amount of air they can push at low RPMs. For example, most 180 mm fans running around 800 to 1000 RPM can outperform 140 mm fans running at 1200 RPM or more. This makes them great for air-cooling hardware at lower noise levels.
200 mm Fans
Like 180 mm fans, 200 mm fans are on the “rare” end of what we’d consider “common,” with only the largest full- and super-tower cases boasting enough room for more than one of these. Even then, they usually only have enough room for a couple of 200 mm intakes, sticking with more traditional 120 and 140 mm fans for the other fans.
The same strengths and weaknesses of 180 mm fans apply here, too. 200 mm fans have great low-RPM performance, but the size and cost constraints mean that you rarely see cases opt for fans this large.
So there you go, a quick run-through of the most common case fan sizes. The 120 and 140 mm fans will be the ones you see most regularly in PC cases and CPU coolers. The smaller and larger ones are for more specific uses, and you’re unlikely to see them very often, if ever.
Already have fans but don’t know what size they are? Check out our guide to measuring fans for a quick way to figure that out. Or if you’re in the market for some new fans for your computer, check out our roundup review of the best case fans.